In the course of accomplishing various construction, maintenance, and supervision tasks, people must often work underground, such as when working in a underground sewer or communications enclosure. These people are required to move vertically downwardly through a confined space entry to a below surface location where the work is to be performed. In other instances, rescue personnel descend through a confined space entry when making a rescue of a person located at some underground location. In many instances, there are no support structures, such as ladders, for supporting a person engaged in underground work or rescue efforts.
Devices have been developed for supporting workers or rescuers descending through a confined space entry to an underground location. For example, Elvin Safety Supply, Inc. markets systems having tripod and davit arm for descent and retrieval of workers through a confined space entry. In the Elvin system a worker is suspended by a cable from the tripod or davit arm device. The use of a suspension cable in this type of descent and retrieval system allows the worker to swing uncontrollably within the underground space, which renders this system unstable for the worker and inadequate for many purposes. Other types of prior art devices embody very large expensive and cumbersome systems used essentially by urban sewer districts for underground work. These large systems also suspend the worker support by cables.
The primary problem with these prior art systems is their incapability of providing stabilized descent, suspension, and retrieval of a worker or rescuer. Therefore, a need exists for a device permitting descent of a worker into an underground space or confined space that provides controlled and stabilized descent, suspension, and retrieval.